A fighter of Libyan forces allied with the U.N.-backed government carries a wounded fighter during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

Fighters of Libyan forces allied with the U.N.-backed government run for cover during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government carries a wounded fighter during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

Fighters of Libyan forces allied with the U.N.-backed government move towards Islamic State fighters positions during a battle in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government shows a disarmed antipersonnel mine planted by Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government fires a rife at Islamic State fighters during a battle in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

Fighters of Libyan forces allied with the U.N.-backed government fire weapons at Islamic State fighters during a battle in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government gestures after other fighters fire artillery at Islamic State fighters during a battle in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

Fighters of Libyan forces allied with the U.N.-backed government move towards Islamic State fighters positions during a battle in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A wounded fighter of Libyan forces allied with the U.N.-backed government runs for cover during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government runs for cover with another fighter while carrying a wounded fighter during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

Pieces of bricks fly off the wall as Islamic State fighters open fire at Libyan forces allied with the U.N.-backed government during a battle in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government runs for cover during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government smokes during a battle with Islamic State fighters in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)

A fighter of Libyan forces allied with the U.N.-backed government looks through a hole in a wall as a self-propelled artillery gun fires at Islamic State fighters during a battle in Sirte, Libya, July 31, 2016. (Photo by Goran Tomasevic/Reuters)